Cross-linked enzyme-polymer conjugates with excellent stability and detergent-enhanced activity for efficient organophosphate degradation

Huan Cheng,Jian-He Xu,Jun Ge,Xun Cao,Qing Dai,Xiao-Jing Luo,Dian-Sheng Xu,Yun-Peng Bai,Xiao-Yan Zhang,Yu-Lian Zhao

doi:10.1186/s40643-018-0236-2

Abstract

BackgroundEnzymatic biodegradation of organophosphate pesticides (OPs) is a promising technology to remove these toxic compounds. However, its application in industrial washing was restricted by the lack of efficient immobilized enzymes that can work at high temperatures and high pHs in the presence of various detergents. Therefore, it is necessary to develop a simple method to prepare a robust immobilized enzyme for efficient degradation of OPs.ResultsAn organophosphate hydrolase (OPH), PoOPHM9, was conjugated and immobilized with a commercially available polymer, Pluronic F127. The prepared cross-linked enzyme-polymer conjugate (CLEPC) displayed higher pH stability in the range from 7.0 to 11.0 and a higher optimal temperature (50 °C) than that of free PoOPHM9 (30 °C). Its half-life and apparent kcat/KM reached 12.8 h at 50 °C and 390.3 ± 7.8 mM−1 s−1, respectively, which were even better than that of the traditional cross-linked enzyme aggregates (CLEA, 7.2 h and 10.9 ± 1.7 mM−1 s−1). The activity of PoOPHM9 CLEPC was further enhanced up to 2.5-fold by the anionic, nonionic and biocompatible detergents, which was first observed. 0.15 mM Malathion was degraded completely by PoOPHM9 CLEPC after activation within 10 min in the presence of 0.1% (w/w) detergents of all types at pH 9.0 and 25 °C, demonstrating its capability in degrading OPs at practically relevant conditions.ConclusionThe conjugation of Pluronic F127 in enzyme immobilization could effectively reduce the activity loss of immobilized enzymes and enhance their stability and activity at high temperatures and high pHs. In addition, the activity of CLEPC can be even enhanced in the presence of various detergents. This technology can be extended easily to produce other immobilized polymer-enzyme conjugates due to its simplicity.

Highlights

Enzymatic biodegradation of organophosphate pesticides (OPs) is a promising technology to remove these toxic compounds
In spite of high activity, free organophosphate hydrolase (OPH) are difficult to be recovered from aqueous solution, and are often denatured quickly under harsh environments such as high temperatures and high pHs that are usually used in industrial washing and water treatment, hindering its usage in practical applications (Giudice et al 2016; Bai et al 2017)
Preparation of PoOPHM9 cross-linked enzyme-polymer conjugate (CLEPC) Previous study demonstrated that the hydrophobic PPO blocks of Pluronic F127 can interact with hydrophobic amino acids such as Phenylalanine (Phe) on the surface of OPH, and physically associate with OPH to form a noncovalent binding enzyme-polymer complex (Kim et al 2014b)

Summary

Introduction

Enzymatic biodegradation of organophosphate pesticides (OPs) is a promising technology to remove these toxic compounds. In spite of high activity, free OPHs are difficult to be recovered from aqueous solution, and are often denatured quickly under harsh environments such as high temperatures and high pHs that are usually used in industrial washing and water treatment, hindering its usage in practical applications (Giudice et al 2016; Bai et al 2017). The immobilized OPHs need to be stable and active at very harsh conditions such as high temperatures and alkaline pH in industrial washing of OP contaminated food. They should bear various detergents that can denature proteins. This special application requirement makes the immobilization of OPHs an extremely difficult task, compared with other immobilized enzymes for traditional biocatalysis

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Conclusion